With the daylight hours getting shorter and the kids going back to school it seems like the freedom of summer has passed. People are a little down here also.
Personally, fall is my favorite time of year. But I certainly understand the concept-- I think a lot of it has to do with the fact that since most employees take their vacation time in the summer, that means after Labor Day they may be working about 10 or more consecutive 5-day work weeks, until Thanksgiving in late November! That is a sobering thought, isn't it?
I don't know what can really be done, but maybe something casual and unofficial that's just specific to your department---perhaps a pot luck lunch once a or twice a month for the fall months?
Or perhaps start a trend of inviting co-workers in your department go out after work every Thursday or Friday for a drink--something to look forward to that they enjoy and will break up the doldrums.